1. Field of the Invention
Solar wind results in a multi-frequency, high energy ionic impingement of the terrestrial poles of the earth. These ions which impinge upon the earth in turn leak from non-pole areas in a weak low noise manner. The leakage provides a measurable paramter which, when recorded, permits the location and identification of surface and subsurface objects or deposits.
The invention generally relates to geophysical prospecting and, more specifically, relates to a method for locating and identifying surface and subsurface objects and deposits, natural and man-made, through sensing, recording and analyzing variations of the earth's vertical electrical alternating current.
2. Description of the Prior Art
Many techniques are known in the prior art to perform geophysical prospecting. For example, Ruehle, et al. in U.S. Pat. No. 3,363,457, teaches that the measurement of radiant energy from subsurface formations enables geophysical prospecting. Weber, in U.S. Pat. No. 4,044,299, teaches a prospecting technique which includes the use of an inductive exciter which induces alternating current energy into the area and structure of the earth which is to be observed. Measurement of the induced current energy allows the determination of the underground environment of the area.
A method and apparatus for measuring subsurface electrical impedance utilizing first and second successively transmitted signals at different frequencies is taught by Madden, et al. in U.S. Pat. No. 3,525,037.
In U.S. Pat. No. 3,942,101, Sayer's geophysical prospecting utilizes a distortion of the atmospheric electrostatic potential gradient which is suggested to be a result of the Nernst effect. Sayer teaches that the distortion provides a means for locating subterranean sources of geothermal energy.
The earth's electromagnetic field also has naturally occurring alterations of the type known as "magnetic noise". Slichter, in U.S. Pat. No. 3,136,943, discloses that such noise is the product primarily of lightening and other electrical discharges and phenomena. Geothermal prospecting can be performed by detecting variations in the naturally occurring electromagnetic radiation from thunderstorms or other phenomena. The detection and measurement of short term variations in the earth's magnetic field for geothermal prospecting is described in U.S. Pat. No. 3,126,510 issued to McLaughlin.
Prospecting can also be performed by comparing the simultaneous variations of the underground electric field and magnetic field to which the circulation of the telluric currents give rise. This comparison of electric field and magnetic field requires the use of electrodes to measure the internal telluric currents in the magnetic field according to Cagniard, U.S. Pat. No. 2,677,801. The solar alternating current is distinguishable over telluric currents for many reasons. Firstly, telluric currents are usually direct currents. Secondly, telluric currents occur only within the earth whereas solar alternating currents eminate from the earth. Thirdly, telluric currents are inconsistent and are not based on ionic impingement of the solar winds. Solar alternating current is based on ionic impingement and has predictable time variations due to its constant directivity (vertical), depth and diurnal character.
In summary, the prior art teaches geothermal prospecting which utilizes variations in the naturally occurring electrostatic potential gradient (Sayer), alternations in the earth's electromagnetic field (Slichter), short term variations in the earth's magnetic field (McLaughlin) and simultaneous variations of the underground electric field and magnetic field (Cagniard). These prior art techniques are in contrast to the present invention which utilizes the vertical alternating current of the earth and frequency modulations due to the alternating electrical current resonance phenomena in the earth.